Habitual speedsters, watch out - new cameras that "know" your average travelling speed are up and running.

Unlike with the spot speed cameras in use here since 1992, motorists will have a much harder time evading the new technology, which calculates a vehicle's average speed over a stretch to determine if it is breaching the speed limit.

Police installed the first set of so-called "average speed cameras" as a trial at Changi Coastal Road last November, and they were switched on in January.

The cameras are mounted on two gantry-like structures about 4km apart and were spotted by The Straits Times, which understands they are capable of monitoring traffic in both directions.